1. Field of the Invention
The present invention relates to a reflection screen apparatus which reflects an image projected by a projection apparatus based on optimal light distribution, and to a projection system using the same.
2. Description of the Related Art
A projector of a so-called front projection type uses a reflection screen that reflects a projected image thereof. Various ideas have been tried for the screen so that a brighter light can be obtained for an observer by converging luminous flux reflected by the screen to the observer and reducing useless light reflected to the outside of the observer's visual field as much as possible. Accordingly, many inventions or commercial products have been presented regarding a reflection screen of high directivity in which the reflected light distribution angle of a screen reflection surface is narrowed. As opposed to a conventional white matte screen of a wide light distribution angle, a silver screen, a pearl screen, a bead screen, a hologram screen, etc., can be cited as such representative screens that have been in practical use. Further, various ideas have been presented to increase directivity by a structure such as a shape of a screen reflection surface, e.g., in Jpn. Pat. Appln. KOKAI Publications Nos. 6-242511, 5-45733, 2000-275755, 10-26802, etc. Thus, since the amount of a light can be increased for the observer in a condensed manner by the screen of a small light distribution angle, a demand therefor tends to increase more and more.
Recently, however, widespread use of projectors has increased the need for projection on a large screen even at a place of limited space, consequently increasing short-focus projectors. Thus, an incident angle of a projected luminous flux made incident on a screen end surface inevitably becomes steep on a general plane screen, creating a situation in which a direction itself of the reflected light distribution thereof is shifted more to an area outside the observer. A problem of the impossibility of achieving an original object occurs even on the screen reflection surface of a small light distribution angle.
Thus, Jpn. Pat. Appln. KOKAI Publication No. 5-297466 presents a screen apparatus that has a mechanism for changing light distribution angle characteristics by bending and deforming the entire screen reflection surface to a predetermined curved surface shape. This screen apparatus sets a plane state when observation is carried out at a wide light distribution angle by many people, and changes its state to a curved surface shape when observation is carried out by a small number of people. Additionally, a surface inspection apparatus or the like based on an image obtained by simply making variable a curvature of a curved surface shape of a screen reflection surface and concentrating a reflected light on a predetermined object is presented in Jpn. Pat. Appln. KOKAI Publication No. 8-114430. According to this method, it is possible to effectively provide bright images to an observer by making effective use of screen reflection characteristics of a small light distribution angle.